A. Field of the Invention
The field of the present invention relates generally to wheel floats, carriages, casters and like apparatuses that are utilized to moveably support a load across a surface. In particular, the present invention relates to wheel floats that moveably and safely support a load across a surface having uneven or irregular areas. Even more particularly this invention relates to wheel floats having a pivot assembly that allows independent articulation of interconnected walking beam assemblies.
B. Background
Casters and carriage assemblies, typically comprising one or more casters, are generally well known and commonly utilized to assist in moving an object from one location to another across a surface. A conventional carriage assembly is attached to, integral with or otherwise configured to support a frame or the like having a support surface on which the object rests or is attached in a manner that allows the user to move the object with much less effort than would otherwise be required. Such carriage assemblies are utilized in numerous types of industry, in the home, in the medical field and, generally, anywhere it is either necessary or desirable to efficiently and safely move an object across a surface. For instance, airplane, automobile and other vehicle factories use carriage assemblies to move engines, frames, transmissions and other components from one part of the factory to another.
Although conventional carriage assemblies, as well as individual casters, tend to function well on smooth surfaces, they generally do not function very well on surfaces that are uneven and/or irregular. Even surfaces that appear to be planar will often, if not usually, have areas where the surface is not planar. For instance, many concrete or other hard, relatively smooth surfaces have one or more expansion joints, door jambs and tracks, markings and the like that must be passed over or crossed to transfer the object, moveably supported by the carriage assembly or caster, across the surface. In addition, conventional carriage assemblies and casters also tend to not function well on surfaces that have small obstructions, such as rocks, screws, bolts and such, on the surface in the path where a wheel of the carriage assembly or caster will traverse. Such objects are commonly found on factory and other floors. As well known, when a wheel of a carriage assembly or caster attempts to pass over an uneven or irregular area of the surface or a small object on the surface, the wheel tends to have difficulty. The difficulty of passing across such an area or over such obstructions is significantly compounded when the load is heavy. Such difficulty can substantially decrease the efficient operation of moving the object.
In addition to the loss of efficiency, the problems associated with moving a heavy object across a surface on a frame or the like supported above the surface by a conventional carriage assembly or caster include the risk of tipping due to the carriages/casters being inherently unstable on uneven and irregular surfaces and surfaces having small obstructions. The risk of tipping is substantially increased when changing directions and under other circumstances, including when the carriage/caster encounters something on the surface that tends to restrict travel in the selected direction. Generally, the instability results from the carriage/caster having a support post that is offset a distance away from the wheel axle. The load supported by the carriage/caster tends to bear down through the support post, which produces a tipping moment relative to the wheel axle. In addition, the angled vector of the weight of the object being moved tends to be higher than the wheel axle and, therefore, will drive the wheel down against the uneven or irregular surface or the obstruction on the surface, making it more difficult to traverse that area or obstruction.
Various carriage assemblies and casters have been devised which are better adapted to move an object, particularly a heavy object, across an uneven or irregular surface and over obstructions on the surface. One such prior art caster is set forth in U.S. Pat. No. 5,507,069, which issued to the inventor of the present invention. The above patent describes an articulated caster having a base assembly with three or more wheels attached thereto and extending radially from the center of the base and a pivot arm having a housing at a lower end that is received in a recessed area of the base. The upper end of the pivot arm connects to the apparatus using the caster. The pivot housing has a spherical chamber that contains a pivot ball. A pivot shaft passes through a pivot hole in the pivot ball, an angled slot in the housing and through a pair of pivot shaft holes provided in the opposing walls of the base recess area. The pivot holes are disposed as low as possible for improved stability. U.S. Pat. No. 7,146,683, U.S. Pat. No. 7,500,285 and U.S. Pat. No. 7,506,405, which also issued to the inventor of the present invention, describe articulated casters comprising a base assembly, at least three wheels pivotally attached to the base assembly, a pivot arm having an upper end configured to attach to an object to be moved and a universal joint at a lower end of the pivot arm that is attached to the base and configured for pivotal motion about two perpendicular axes. A brake assembly, attached to the pivot arm, forces a brake pad into frictional engagement with a surface to place the brake assembly in its engaged position. These patents also describe combining multiple casters together to form a compound carriage system to support larger and/or heavier loads without excessive elevation of such loads and describe a carriage system wherein the load is carried on a load supporting section of a frame between pairs of carriages.
One known disadvantage of prior art carriage assemblies and casters, including those described above, is that the components thereof require varying degrees of machining, welding and/or break bending to configure the carriage/caster for use with a frame to move an object across a surface. As is well known, such operations increase the cost of assembling the carriage/caster, both in materials and in labor, and result in structural weak points that can fail or otherwise reduce the useful life of the carriage/caster. In certain circumstances, the impact of these operations can significantly impact the cost and life of the carriage/caster. In addition to increasing the initial cost, the manner in which prior art carriages and casters are configured makes it difficult and relatively expensive to repair any parts that fail or replace any parts that have worn.
An improved articulating carriage that solves many of the problems identified above is set forth in U.S. patent application Ser. No. 12/754,593 (the “'593 application”), which inventors include the inventor of the present application and of which the present application is a continuation-in-part. The '593 application describes an articulating carriage that is specially configured to support an object so as to facilitate safe and efficient movement of the object across a surface area having one or more non-planar obstructions. As set forth therein, the walking beam pivotally supports a pedestal, which provides a support surface to support the object. The walking beam pivots relative to the pedestal as the object passes over the non-planar areas. The '593 application also describes an articulating carriage having a pair of walking beam assemblies connected by a crosstube that pivotally supports the pedestal.
While the above patents and the invention of the '593 application represent a substantial improvement over prior art casters, there is still a need for an improved wheel float for use to move objects across an uneven or irregular surface and across a surface having small obstructions in the path of the carriage. Specifically, what is needed is a wheel float that is more effective and efficient at moving an object, particularly heavy and/or large objects, across a surface which is uneven or irregular or which contains obstructions that could impede the movement of the carriage. The preferred wheel float should be configured such that it drives the wheels over any uneven or irregular areas and any obstructions, it is stable while going over such areas or obstructions and it is relatively close to the surface for ease of loading and unloading the object from a frame having the improved carriage. Preferably, the wheel float should be configured such that it can be assembled without machining, welding or break bending of any components to reduce the cost of such assembly and the need for expensive skilled labor. The preferred wheel float should be adaptable for use with a carriage system that can efficiently and safely move large and/or heavy objects across a surface.